Method of evaluating green malt qualities by electron spin resonance spectrometry and method of evaluating malt qualities

ABSTRACT

A method is provided in which a correlation is made between a parameter indicating modification of a sampled malt in a germination process in which barley is germinated, and an ESR signal intensity of the sampled malt. The parameter is determined, in advance, by general analytical methods including chemical analytical methods. The ESR signal intensity is determined by measuring a peak height of spectrum of the sampled malt at a g value at which an unpaired electron derived from a carbon radical is resonant. The ESR signal intensity is a ratio of the measured peak height of spectrum to a peak height of spectrum of a reference, per a unit weight of the sampled malt. The modification state of the sampled malt can be evaluated based on the ESR signal intensity determined by electron spin resonance spectrometry. Kohlbach index, Hartong index at 45° C., diastatic power, β-glucan content, viscosity, and friability may be used as the parameter.

TECHNICAL FIELD

[0001] The present invention generally relates to a quality evaluationmethod of malt to be used in the production of malt alcoholic beveragessuch as beer, and, more particularly, to a quality evaluation method ofmalt using Electron Spin Resonance (ESR) analysis.

BACKGROUND ART

[0002] Beer is mainly made of barley malt that serves as the source ofstarch and enzyme. The production process of beer is classified into amalting process, a brewing process, and a packaging process. In themalting process, malt is steeped into water for germination. Duringgermination, degradative enzymes are activated. The germinating barleyis called green malt. After germinating to an expected extent ofmodification, green malt is dried (kilned). In the next brewing process,water is added to ground malt and is heated for saccharification, andthen, is filtered. The filtered liquid is boiled after adding hop, andsaccharified liquid (wort) is obtained by separating hop dreg. Aftercooling, the wort is fermented by adding yeast, and is stored at a coldtemperature. After carbon dioxide generated during the storage isdissolved into the fermented liquid (beer), and flavor is matured, thebeer is filtered. In the packaging process, the beer is antisepticallyfiltered and is contained in barrels and/or bottles for distribution.

[0003] The quality of beer heavily depends on the quality control of themalting process, that is, the quality of produced malt. In general, agerminating process takes about four to six days. During germination,enzymes are synthesized, and starch and protein are partially degraded.The grade of malt degradation is referred to as “modification”.

[0004] In the production process of beer, it is important to control themalt quality. Kohlbach Index, Hartong index at 45° C., diastatic power,viscosity, and β-glucan content are indexes that indicate the quality ofmalt. These parameters are controlled in the malting process to maintainconstant malt quality.

[0005] The parameters for indicating malt modification are describedbelow.

[0006] Kohlbach Index: the ratio of the nitrogen amount of congress wortprepared for analysis and the nitrogen amount of the whole malt. Itindicates the extent of protein degradation in the malt. The higher theKohlbach Index is, the more the malt is degraded. (modified).

[0007] Hartong index at 45° C.: the ratio of the extract of 45° C.,1-hour mashing of fine ground malt and the extract of the congress wort.The amount of extract mainly depends on the amount of starch and sugar.In malt, the degradation of protein components existing among starchparticles affects the amount of extract. Accordingly, Hartong index at45° C. indicates the degradation grade of both starch and protein. Thehigher the Hartong index at 45° C. is, the more the malt is modified.

[0008] Diastatic power: To determine the starch degradative enzyme powerof malt, the amount of reduced sugar generated by affectingwater-extraction liquid of malt to soluble starch is measured usingiodometry. The starch degradative enzymes are synthesized as the barleygerminates. In a brewing process, these enzymes are required fordegradation of starch in malt and in adjuncts (for example corn starch).Malt with low diastatic power may cause a problem in a beer brewingprocess.

[0009] β-glucan content: β-glucan is the degradative product of cellwall of the malt. If the cell wall is not degraded enough, the lauteringof mash becomes not smooth. Beer with high β-glucan content may causehaze after freezing.

[0010] The β-glucan content is measured as follows: after ground malt isheated in ethanol to inactivate enzyme, β-glucan in the malt is degradedto glucose by processing with lichenaze and β-glucosidase; and theamount of generated glucose is determined usingglucoseoxidase/paroxidase method.

[0011] Viscosity: the viscosity of congress wort prepared for theanalysis. Polysaccharides such as starch, dextrin, β-glucan, andpentosan mainly affect the viscosity of wort. The viscosity indicatesthe degree of degradation of stored starch and cell wall. The lower isthe viscosity, the more the malt is moderated. The viscosity is measuredat 20.00° C. with Ubbelohde type viscometer.

[0012] Friability: Friability is measured by a dedicated friabilitymeter. Specifically, the friability is measured as follows. After beingground with a roller, malt samples are separated into one that passesthrough a specific slit and one that does not pass through the specificslit and remains. The separated malt samples are measured. Thefriability of the malt samples is defined as the ratio between theseparated malt samples. Malt of which starch and cell wall are not welldegraded is crystalline and consequently hard. Friability of such maltis low. Well degraded malt is mealy and easy to grind. The friability ofsuch malt is high.

[0013] Conventionally, the above parameters for analyzing themodification of malt are determined with general analytical methods suchas chemical analysis. However, the general analytical methods haveproblems such that the preparation and measurement of samples requireconsiderable time. A rapid and simple analytical technique for maltquality evaluation is needed.

[0014] There are many analytical techniques for analyzing material, suchas chemical analysis, optical analysis, and physical analysis (usingX-ray, for example). Recently, electron spin resonance (ESR) analysis isdrawing attention as an analytical technique to obtain molecular levelinformation of material. The application of ESR analysis is beingintensively studied.

[0015] The principle of ESR is exactly the same as that of nuclearmagnetic resonance (NMR). ESR is a kind of magnetic resonance spectrum.Whereas the NMR measures the resonant absorption of nuclear spins, theESR measures the resonant absorption of electron spins. The ESR mostdirectly reveals information about the molecular structures and electronstates of materials having unpaired electrons such as a radical and atransition metal complex (trivalent iron ion and bivalent copper ion,for example). As of now, the ESR is the most reliable analyticaltechnique for detecting radicals.

[0016] ESR spectra show the following: g value indicating the positionof resonance of the unpaired electrons, resonance intensity indicatingthe number of unpaired electrons, absorption width related to relaxationtime, and hyper fine structure caused by the coupling between theunpaired electrons and atoms (¹H and ¹⁴N, for example) having nuclearspin near the unpaired electrons. Since each of radical species exhibitsan intrinsic position of absorption, one can identify the radicalspecies based on the g value. Additionally, one can consider reactiontime and reaction mechanism based on the change over time of absorption(intensity).

[0017] The inventors intensely studied the application of ESR to theevaluation of state (quality) of malt in beer brewing. As a result ofthe study, the inventors discovered that, if an absorption intensity(signal intensity) is observed, the radical species is roughlyidentifiable based on the g value, and that there is a correlationbetween the absorption intensity (signal intensity) and the state(quality) of green malt and malt. The present invention, which is madebased on the above discovery, provides a more rapid and simpler methodof evaluating the quality of malt, than that of conventional analyticaltechniques.

SUMMARY OF THE INVENTION

[0018] The above problems can be solved by means of the presentinvention described below.

[0019] According to an aspect of the present invention, a qualityevaluation method of green malt sampled in a germinating process ofbarley by electron spin resonance (ESR) spectrometry, includes the stepsof: measuring a peak height of spectrum at a g value at which anunpaired electron derived from a carbon radical is resonant; determiningan ESR signal intensity that is a ratio of the measured peak height ofspectrum to a peak height of spectrum of a reference, per a unit weightof the sampled green malt; and evaluating a germination state of saidsampled green malt by comparing the determined ESR signal intensity witha predetermined reference level.

[0020] The present invention makes it possible to determine the ESRsignal intensity of green malt samples by using an electron spinresonance method, and to evaluate the quality of green malt samplesbased on the determined ESR signal intensity.

[0021] According to a second aspect of the present invention, aquality-evaluation method of malt sampled in a germinating process ofbarley by electron spin resonance (ESR) spectrometry, includes the stepsof: measuring a peak height of spectrum at a g value at which anunpaired electron of a carbon radical is resonant; determining an ESRsignal intensity that is a ratio of the measured peak height of spectrumto a peak height of spectrum of a reference, per a unit weight of thesampled malt; and evaluating a modification of the sampled malt bycomparing the determined ESR signal intensity with a predeterminedreference level.

[0022] The present invention makes it possible to obtain the ESR signalintensity of malt samples by using an electron spin resonance method,and to evaluate the quality of the malt samples based on the ESR signalintensity.

[0023] According to a third aspect of the present invention, anevaluation method of modification of malt sampled in a germinationprocess of barley, includes the steps of: determining, in advance, acorrelation between a parameter measured by general analytical methodsincluding chemical analytical methods, said parameter indicatingmodification of the sampled malt, and an ESR signal intensity of thesampled malt, the ESR signal intensity being determined by an electronspin resonance spectrometry whereby a peak height of spectrum of saidsampled malt is measured at a g value at which an unpaired electron of acarbon radical is resonant, and the ESR signal intensity is a ratio ofthe measured peak height of spectrum to a peak height of spectrum of areference, per a unit weight of the sampled malt, and evaluating saidmodification of the sampled malt based on said parameters determinedusing the corresponding ESR signal intensity determined by said electronspin resonance spectrometry.

[0024] The present invention makes it possible to determine the ESRsignal intensity of malt samples by using an electron spin resonancemethod, and to estimate parameters indicating the modification of maltbased on the determined ESR signal intensity. Accordingly, the qualityof malt can be evaluated.

[0025] At least one of a Kohlbach index, Hartong index at 45° C.,diastatic power, β-glucan content, viscosity, and friability is used asthe parameter for indicating the modification of malt.

BRIEF DESCRIPTION OF DRAWINGS

[0026]FIG. 1 is a graph showing an ESR spectrum of green malt;

[0027]FIGS. 2A and 2B are charts showing the effect of steep-outmoisture and germination time on the ESR signal intensity of green malt;

[0028]FIG. 3 is a chart showing the effect of germination time on theESR signal intensity of malt; and

[0029]FIGS. 4A through 4F are charts showing the correlation betweenvarious parameters and the ESR signal intensity of malt.

BEST MODE FOR CARRYING OUT THE INVENTION

[0030] Embodiments of the present invention are described in more detailbelow. The outline of the ESR analyses performed by the inventors isdescribed first.

[0031] (1) Barley, Malt Sample

[0032] If much moisture is contained in the sample, the moisture absorbsthe electron spin resonance. When solid samples containing much moistureare measured with an ordinary ESR analysis method, the moisture needs tobe removed. Accordingly, green malt was used after being lyophilized, asa sample for the analysis of germinating barleys (green malt). However,since malt contains low enough moisture, the malt was used as a samplewithout being lyophilized.

[0033] Japanese “Amagi Nijo” barleys and Canadian “Kendall” barleys wereused as the samples. They were malted with a 90 kg-scaled pilot maltingplant. The barleys were steeped in water at 14° C. and were germinatedat 14° C. Malt with different germination time was prepared using an 8kg-scaled kilning apparatus.

[0034] (2) ESR Analysis

[0035] The ESR analysis was carried out at the following measuringconditions.

[0036] Temperature of sample: room temperature

[0037] Sweep time: 60 seconds

[0038] Modulation width: 0.1 mT

[0039] Microwave power: 10.63 mW

[0040] Sweeps/measurement: 1 time

[0041] Internal standard: Mn²⁺

[0042] Five whole grains of green malt and malt (0.4 g), or about 0.2 gof ground samples of them were put in an ESR sample tube (cylindricaltube), and their electron spin resonance absorption was measured with anelectron spin resonance spectrometer. After the measurement of g valuebased on measured spectra, the signal intensity was calculated as therelative ratio of the peak height of the sample to the peak height ofMn²⁺ used as the internal standard. The ESR signal intensity is definedas the relative height per a unit weight of sample (/g). One sample wasmeasured 5 times and obtained data were averaged.

[0043] (3) ESR Preparatory Analysis of Green Malt and Malt

[0044]FIG. 1 is a graph showing an ESR spectrum of ground green malt.

[0045] As is shown in FIG. 1, the spectrum shows a singlet peak at theposition of g=2.0049. The g value g=2.0049 means that this spectrum iscaused by carbon radicals. It is well known that, in food samples, whichcontain lipids and proteins (amino acid), for example, free radicalsgenerated by the oxidation of lipids take hydrogen from the proteins andgenerate stable organic radicals derived from proteins, and that theyproduce a singlet peak around g=2.00. Accordingly, the inventorsspeculate that this peak is also caused by stable organic radicalsderived from proteins in the green malt. In addition, ground maltsamples and whole grain samples of malt and green malt (without grind)showed similar spectra pattern.

[0046] (4) Change in ESR Signal Intensity of Green Malt DuringGermination

[0047] Another experiment was performed to determine change in the ESRspectrum (signal intensity) of green malt during malting (germination).

[0048]FIGS. 2A and 2B show the results of ESR measurement of thelyophilized green malt sampled once a day after germination andlyophilized. FIG. 2A shows the result of whole grains of green maltmalted with two different steep-out moisture levels of 37% and 43%, andFIG. 2B shows the result of ground green malt malted with steep-outmoisture levels of 37% and 43%.

[0049] These experimental results show that, as germination time passes,the ESR signal intensity increases. The results also show that thehigher is the steep-out moisture level, the higher is the ESR signalintensity. Accordingly, it is found that the germination state of barleycan be evaluated based on the ESR signal intensity.

[0050] From a comparison between the whole grain samples and groundsamples, the ESR signal intensity of green malt increased with grind.This increase in ESR signal intensity could be derived from the increasein radicals by oxidation during grinding.

[0051] Based on the above experimental results, the inventors speculatethat the amount of radicals is increased during germination because thegermination activates the respiration of barley and consequently, theoxidation of ingredients contained in the barley, and accelerates thegeneration of stable organic radicals derived from proteins. Only thesignal intensity changed with the germination time in the spectra. Nonew peak is observed in the spectra. The increase in stable organicradicals derived from proteins during germination is an interestingdiscovery in view of various changes of ingredients including thesynthesis of enzyme in germinating barley. This discovery is expected tobring a new angle into the study of botanical germination.

[0052] (5) Relationship Between ESR Signal Intensity and Malt Parameters

[0053] Other green malts germinated for one through six days were kilnedinto malts and ground. The ESR signal intensities of the ground maltswere compared.

[0054]FIG. 3 shows the result of the above experiment. As is shown inFIG. 3, the ESR signal intensity increased with germination time. Basedon this result, the inventors confirmed that the increase in the ESRsignal intensity of green malt with germination time is retained evenafter kilning.

[0055] The correlation between several typical parameters indicatingmalt modification and the ESR signal intensity was studied. FIGS. 4Athrough 4F show the relationship between the parameters indicating maltmodification and the ESR signal intensity of malt samples used for themeasurement shown in FIG. 3. FIGS. 4A through 4F show the relationshipof malt quality parameters, that is, Hartong index at 45° C. (FIG. 4A),viscosity (FIG. 4B), β-glucan content (FIG. 4C), friability (FIG. 4D),diastatic power (FIG. 4E), and Kohlbach index (FIG. 4F), respectively,with the ESR signal intensity.

[0056]FIG. 4A shows that Hartong index at 45° C. increases with signalintensity less than 9.5, and remains constant with signal intensity of9.5 or more.

[0057]FIG. 4B shows that viscosity is constant with signal intensity of12 or more.

[0058]FIG. 4C shows β-glucan content does not remain constant over wholerange of signal intensity.

[0059]FIG. 4D shows that friability remains constant with signalintensity of 9 or more.

[0060]FIG. 4E shows that the diastatic power remains constant withsignal intensity of 9 or more.

[0061]FIG. 4F shows that Kohlbach index remains constant with signalintensity of about 9 or more.

[0062] The results of the above experiments confirm that malt with ESRsignal intensity between 9 and 15 is modified enough and satisfies thegeneral requirement level of malt quality.

[0063] According to the above experimental results, germination state ofmalt can be estimated and evaluated based on the ESR signal intensity ofthe germinating malt (green malt).

[0064] The modification and/or diastatic power of malt can be evaluatedby sampling green malt or malt during malting, and measuring ESR signalintensity using the ESR analysis. If the ESR signal intensity is equalto or more than a specific level, the malt quality can be guaranteed.Such a quality evaluation method can be used as a rapid and simplemethod to check the malt quality.

[0065] The ESR analysis of malt does not require lyophilizing the maltsample. The malt sample is ground and put in an ESR sample tube. Themeasurement by the ESR spectrometer takes less than two minutes.Although the setting of the ESR spectrometer takes about 30 minutes, theESR analysis requires substantially less time than conventional methoddoes. The preparation of malt samples is quite easy too.

[0066] Preferred embodiments of the present invention are described indetail above. However, the present invention is not limited to theseembodiments, and variations and modifications may be made withoutdeparting from the scope of the present invention.

[0067] As is apparent from the above detailed description, the presentinvention makes it possible to evaluate the quality of green malt basedon the ESR signal intensity of green malt sample using electron spinresonance method.

[0068] The present invention also makes it possible to evaluate thequality of malt based on the ESR signal intensity of malt sample usingthe electron spin resonance method.

[0069] Additionally, the present invention makes it possible to estimateparameters indicating malt modification such as Kohlbach index, Hartongindex at 45° C., diastatic power, β-glucan content, viscosity, andfriability based on parameters measured by the electron spin resonancemethod.

1. A quality evaluation method of green malt sampled in a germinationprocess of barley by electron spin resonance (ESR) spectrometry,comprising the steps of: measuring a peak height of spectrum at a gvalue at which an unpaired electron derived from a carbon radical isresonant; determining an ESR signal intensity that is a ratio of themeasured peak height of spectrum to a peak height of spectrum of areference, per a unit weight of the sampled green malt; and evaluating agermination state of the sampled green malt by comparing the determinedESR signal intensity with a predetermined reference level.
 2. A qualityevaluation method of malt sampled in a germination process of barley byelectron spin resonance (ESR) spectrometry, comprising the steps of:measuring a peak height of spectrum at a g value at which an unpairedelectron derived from a carbon radical is resonant; determining an ESRsignal intensity that is a ratio of the measured peak height of spectrumto a peak height of spectrum of a reference, per a unit weight of thesampled malt; and evaluating a modification state of the sampled malt bycomparing the determined ESR signal intensity with a predeterminedreference level.
 3. An evaluation method of modification state of maltsampled in a germination process of barley, comprising the steps of:determining, in advance, a correlation between a parameter measured bygeneral analytical methods including chemical analytical methods, saidparameter indicating a modification state of the sampled malt, and anESR signal intensity of the sampled malt, the ESR signal intensity beingdetermined by an electron spin resonance spectrometry whereby a peakheight of spectrum of said sampled malt is measured at a g value atwhich an unpaired electron of a carbon radical is resonant, and the ESRsignal intensity is a ratio of the measured peak height of spectrum to apeak height of spectrum of a reference, per a unit weight of the sampledmalt, and evaluating said modification of said sampled malt based onsaid parameters determined using the corresponding ESR signal intensitydetermined by said electron spin resonance spectrometry.
 4. Theevaluation method as claimed in claim 3, wherein said parameter is atleast one of a Kohlbach index, Hartong index at 45° C., diastatic power,β-glucan content, viscosity, and friability.